1. Field of the Invention
The present invention relates to a sheet processing device performing a process such as a sheet center-folding process and an image forming system including the sheet processing device.
2. Description of Related Art
Conventionally, devices have been proposed to perform a sheet processing including the sheet center-folding process.
Japanese Patent Application Laid-Open No. 2005-96913 discloses technology that changes the posture of a sheet, and then performs a center-folding process and a saddle-stitching process. In Japanese Patent Application Laid-Open No. 2005-96913, a manner of changing the sheet posture so as to achieve rapid and reliable changes in sheet posture with respect to various sheet sizes has been proposed.
Japanese Patent Application Laid-Open No. 2011-111243 discloses a device that forms a fold along a direction orthogonal to a sheet feed-in direction, and that feeds a sheet along the direction of the fold (i.e., the direction orthogonal to the feed-in direction).
On the other hand, the device disclosed in Japanese Patent Application Laid-Open No. 2005-96913 changes the posture of a sheet three times. Accordingly, because a mechanism for changing the posture of the sheet is complicated and extra space is required to change the posture of the sheet, it is thought that the device is more susceptible to increase in size.
In contrast, a device for forming a fold in a sheet along a direction orthogonal to the feed-in direction of the sheet and feeding the sheet along the direction of the fold, such as that disclosed in Japanese Patent Application Laid-Open 2001-111243, is not required to change the posture of the sheet much at all, and therefore is preferable because its configuration can be miniaturized.
However, the sheet processing device disclosed in Japanese Patent Application Laid-Open 2011-111243 is a device which is specialized to fold sheets. Thus, it is thought that the device may be practically insufficient as a finisher for an image forming device such as a copy machine and a laser beam printer. In other words, when the device is employed as the finisher for the image forming device, it is convenient if a mode for saddle-stitching or a mode for ejecting the sheet as it is can be selected in addition to a mode for center-folding the sheet.
However, with respect to conventional sheet processing devices which include the one disclose in Japanese Patent Application Laid-Open 2011-111243, a configuration which is capable of combining both a sheet center-folding process and a process other than center-folding (e.g., the type of arrangement of a part performing the center-folding and a part performing a process other than the center-folding within the device, and the manner in which sheets are fed) has not been sufficiently considered. Depending on an arrangement and feeding path, a problem may arise where the feeding path becomes complicated, thereby complicating and increasing the size of the overall configuration of the apparatus, and also the fractional sound of a sheet at the time of feeding.